1. The Field of the Invention
The present invention relates to a satellite signal receiver, and in particular, to a power controller for a satellite signal receiver used for devices, such as mobile terminals or mobile phones, that have a satellite signal reception unit.
2. Related Art
One conventional satellite signal receiver is known by Japanese Patent Laid-open Publication No. 8-304526, of which configuration is illustrated by FIG. 1.
The satellite signal receiver shown in FIG. 1 includes a positional information generator 1, operational command receiver 2, power supply 3, and power switching unit 4 that turns on or off power of the positional information generator 1.
The positional information generator 1 is equipped with an receiving antenna 5 for receiving electric waves that has been transmitted from satellites, satellite receiver 6, positional data output circuit 7, and transmitting antenna 8. The satellite receiver 6 demodulates a signal of the received electric waves to computes a current position of this apparatus. The operational command receiver 2 includes a receiving antenna 9 for receiving in wireless an operational command that has been received from the manager, and a reception circuit 10 via the receiving antenna 9.
When the receiver is in operation, only the power of the operational command receiver 2 is turned on to wait for receiving an operational command from the manager. When the manager transmits an operational command, the operational command receiver 2 receives the operational command and activates the power switching unit 4 so that it turns on. This unit 4 operates to supply the power from a power supply 3 to each element of the positional information generator 1, so that each element is energized. The satellite receiver 6 demodulates each satellite signal supplied from the antenna 5 in such a manner that a current position of this receiver is computed based on the signals from a plurality of satellites. The computed positional data are the subject to demodulation in the positional data output circuit 7, before being sent to the manager via the transmission antenna 8.
After the positional information generator 1 generates positional data, the power switching unit 4 will be kept to be on for a certain time, intermittently, or until receiving a command for stopping the operation. During the period of the on-state of the power switching unit 4, the generator 4 generates positional data.
According to this satellite signal receiver, if there is no need for demands for positional information, powering a main part of the apparatus is stopped, while the power is prepared whenever it is necessary. Hence consumption of useless power is suppressed.
However, the foregoing satellite signal receiver is configured so that an external command controls the turn on/off of power of the satellite receiver 6. Therefore, even when this receiving apparatus is located such that it is impossible for this apparatus to receive satellite electric waves or it is extremely difficult for this apparatus to perform such reception, thereby positioning being impossible, the external command causes the satellite receiver to be activated. This results in that the power is consumed uselessly.